The death of Conrad Bain at age 89 has hit no one harder than Todd Bridges, who for eight seasons played adopted son to Bain’s millionaire character Mr. Drummond on the hit NBC sitcom “Diff’rent Strokes.”

Now the sole survivor of the show’s core cast — Dana Plato committed suicide in 1999, and Gary Coleman died after falling down a flight of stairs in 2010 — Bridges says he’ll miss the man who was his surrogate father both on and off the screen.

“This is probably one of the most heart-wrenching days I’ve had in a long time,” Bridges, now 47, tells The Hollywood Reporter. “That Conrad’s not going to be around anymore to talk to. Whenever I needed advice, I’d call Conrad.”

The two first met in 1977, when a 12-year-old Bridges — who had already starred alongside Abe Vigoda on ABC’s “Barney Miller” spinoff, “Fish” — was cast with Bain and Coleman to star in a 20-minute presentation for NBC executives. The chemistry between the trio was so effortless, the network brass bought a full season on the spot.

“First time in history they bought 26 shows based on a presentation like that — a balcony scene that me, Conrad and Gary worked on together,” Bridges recalls.